Audio Systems: buttons stick on car radio, phillips screw driver, small screws

Question
I bought a used 1998 Toyota Camry 4 cyl with no radio/sound system, just a hole. I found an original equipment radio/tape/CD set (salvaged, I'm sure) on ebay, and it does work well. The only problem is the first 2 of 6 pre-set buttons stick HARD, then after managing to push it in, it is loose for a few minutes, then sticks again. My first thought is something spilled in there and it is sticky inside. What about spraying carefully and lightly with WD-40 into the cracks? That's the best I can come up with.  Any ideas? Thanks alot!

Answer
the face needs to be remove from the radio
it is simple to do and them you need to remove the electronic board with a small Phillips screw driver there are a lot of small screws
then just soap and water to clean all the plastic parts
good luck